Google have not been very good with that. For a long time they didn't back up at all which meant if you swapped phones and didn't manually copy over you lost the codes. Now if you click the default OK button if copies all the codes to Google cloud which is ok if you don't have much money being protected but if you do there's a vulnerability that hacking your Google account gets your TOTP codes and probably passwords if you save them in Chrome. I'm currently in that situation and will probably shift to some other provider so it becomes two things to hack rather than one again.

The problem is logging into your Google account without your 2FA device or phone number.

The answer in all these cases is having more than one option enabled. I just recently tested my Google and Apple login simulating a loss of phone and computer. It was tough but there are options (e.g. Apple lets a friend be your full 2FA, so you can even recover encrypted data)